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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Cs 3 Bi 2 I 9 -hydroxyapatite composite waste forms for cesium and iodine immobilization

Perovskite-based ceramic composites were developed as potential waste form materials for immobilizing cesium (Cs) and iodine (I) with high waste loadings and chemical durability. The perovskite Cs 3 Bi 2 I 9 has high Cs (22 wt%) and I (58 wt%) content, and thus can be used as a potential host phase to immobilize these critical radionuclides. In this work, the perovskite Cs 3 Bi 2 I 9 phase was synthesized by a cost effective solution-based approach, and was embedded into a highly durable hydroxyapatite matrix by spark plasma sintering to form dense ceramic composite waste forms. The chemical durabilities of the monolithic Cs 3 Bi 2 I 9 and Cs 3 Bi 2 I 9 -hydroxyapatite composite pellets were investigated by static and semi-dynamic leaching tests, respectively. Cs and I are incongruently released from the matrix for both pure Cs 3 Bi 2 I 9 and composite structures. The normalized Cs release rate is faster than that of I, which can be explained by the difference in the strengths between Cs-I and Bi-I bonds as well as the formation of insoluble micrometer-sized BiOI precipitates. The activation energies of elemental releases based on dissolution and diffusion-controlled mechanisms are determined with significantly higher energy barriers for dissolution from the composite versus that of the monolithic Cs 3 Bi 2 I 9 . The ceramic-based composite waste forms exhibit excellent chemical durabilities and waste loadings, commensurate with the state-of-the-art glass-bonded perovskite composites for I and Cs immobilization.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1977

Variable temperature pressure cell for polycrystalline X-ray studies down to 2 K - Application to Bi

A variable pressure diamond anvil cell is described for operation at temperatures continuously variable from 300 down to 2 K and controllable within 10 mK. Polycrystalline X-ray data are collected from the pressure cavity by means of either (1) standard photographic techniques, (2) diffractometer measurements, or (3) energy dispersive diffractometry. The facility has been used to examine parts of the phase diagram of Bi. Results from this study indicate that the Bi-I and Bi-III structures are retained to low temperatures; however, there is no evidence to support a structural transition from Bi-V to Bi-VIII.

Skelton, E. F.↗
DOE OSTI2020

Materials Data on BiI3 by Materials Project

BiI3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Bi3+ is bonded in a body-centered cubic geometry to eight equivalent I1- atoms. All Bi–I bond lengths are 3.52 Å. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded in a body-centered cubic geometry to eight equivalent I1- atoms. All I–I bond lengths are 3.52 Å. In the second I1- site, I1- is bonded to four equivalent Bi3+ and four equivalent I1- atoms to form a mixture of distorted edge, corner, and face-sharing IBi4I4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y3Bi by Materials Project

Y3Bi is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Y is bonded to eight equivalent Y and four equivalent Bi atoms to form distorted YY8Bi4 cuboctahedra that share corners with twelve equivalent YY8Bi4 cuboctahedra, edges with eight equivalent BiY12 cuboctahedra, edges with sixteen equivalent YY8Bi4 cuboctahedra, faces with four equivalent BiY12 cuboctahedra, and faces with fourteen equivalent YY8Bi4 cuboctahedra. All Y–Y bond lengths are 3.46 Å. All Y–Bi bond lengths are 3.46 Å. Bi is bonded to twelve equivalent Y atoms to form BiY12 cuboctahedra that share corners with twelve equivalent BiY12 cuboctahedra, edges with twenty-four equivalent YY8Bi4 cuboctahedra, faces with six equivalent BiY12 cuboctahedra, and faces with twelve equivalent YY8Bi4 cuboctahedra.

36 MATERIALS SCIENCE↗